Dear Researchers and Data Managers,

Linking Research Data Files to the National Death Index (NDI)

The NDI is a database containing a set of identifying information of Australian deaths and enables a quick and efficient electronic search of death records registered in Australia since 1980. If a project has obtained approval to link the underlying study or research data file (cohort file) to the NDI, a researcher is able to identify who on the cohort file has potentially died. The researcher can potentially add date and cause of death information to identified deaths on the research file.

This information has been compiled to provide you with an overview of all the steps involved and issues to consider, if you plan to undertake a NDI linkage. It provides information on the NDI and how to prepare a data file for linkage.

This package comprises four sections: 1. A guide or checklist of the steps involved and issues to consider when undertaking a NDI linkage 2. A description of the NDI 3. What to consider when preparing an AIHW ethics application to obtain approval to access NDI data 4. How to supply data in the best form for quick and efficient linkage to the NDI

If you have any questions about linking research data files to the NDI, please contact the AIHW Data Integration Services Centre (DISC) at [email protected].

For questions related to ethics applications, please contact [email protected] or call (02) 6244 1260.

1. Guide/checklist of steps involved and issues to consider when undertaking a NDI linkage Below is a description of the steps involved and issues to consider, if you decide to undertake a NDI linkage:

1. Please read this information package carefully to ensure your project is in scope and that you have enough variables to enable a successful linkage. If unsure, please contact DISC to discuss the scope of your project.

2. Contact DISC if you require a preliminary quote on the costs of the linkage to include in your funding application. Please note that any quote given at this stage is merely an estimate. A final quote will be provided to you, once we are ready to start working on your project and have established the quality of the data provided and the amount of administrative work involved for your project. The minimum cost of a standard, single NDI linkage is $3,500 (excluding GST). If a project requires multiple linkages throughout the lifetime of the project, a linkage fee is charged at the completion of each separate linkage.

3. Before a linkage can be undertaken, you will require approval from AIHW’s Ethics Committee (the Committee). Applications to the Committee are made using EthOS, the AIHW online ethics application portal. EthOS can be accessed via the following link https://ethos.aihw.gov.au. Once the Committee has considered your application, you will receive a letter notifying you of the outcome. If the application is approved, the letter will include details how to contact DISC to obtain the approved linkage.

4. Please note that a separate ethics administration fee is also charged when an application is submitted to the AIHW Ethics Committee.

5. To obtain further information or for assistance with the ethics application, including due dates for applications, please refer to the webpage www.aihw.gov.au/ethics. Section 3 of this document covers some matters to consider when completing an ethics application.

Please note that it is an ethical and legal requirement that AIHW is informed of all persons who require access to NDI information as part of an approved project. The EthOS application requires that the names and signatures of all persons who require access to NDI information are provided, and that they all sign the Undertaking of Confidentiality (i.e. s.29 form). DISC is unable to send the NDI linkage result files to individuals (researchers) who haven’t signed an Undertaking of Confidentiality (s29 form). If a new person joins the research team and requires access to the NDI data (after you have submitted the application to the AIHW Ethics Committee), you will need to submit a completed amendment form and a s.29 form to [email protected]. The Committee will consider the request and you will be notified by letter of the outcome. For assistance with the s.29 and amendment forms and to obtain

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information on due dates for submission, please contact [email protected]. To access an amendment form refer to the webpage http://www.aihw.gov.au/ethics/how-to-use-ethos .

6. Once you receive ethics approval for your linkage request, contact the Data Integration Services Centre (DISC) at [email protected] to obtain instructions how to format and submit your data file for linkage. You will require access to the AIHW Secure Messaging system (ASM) to transfer your data file securely to us. Section 4.3 specifies the variables that are required to undertake a NDI linkage.

7. DISC staff will confirm receipt of the data file and will add your project to the NDI linkage request queue. Please note that there may be a few weeks of delay between DISC receiving the data file and DISC being able to start working on your linkage request. This is dependent on how many other projects are on the queue at that time. A linkage officer will contact you when your project has moved to the top of the DISC linkage queue and when we are ready to start working on your linkage request. A final quote will be provided once a record linkage officer has established the quality of the data supplied and the amount of administrative work involved for your project. The linkage officer will check and prepare the data file for linkage and will inform you of any data issues (if applicable) that need to be resolved.

8. Linkage work will commence, once: • your project has moved to the top of the NDI linkage queue; • any applicable data issues have been resolved; and • the record linkage officer has received an email confirming that the final quote has been accepted.

9. Once the NDI linkage work has been completed, the results will be sent to the relevant researcher (refer to Section 4.6) via the AIHW Secure Messaging system (ASM). Please note that we can only send linkage result files to persons who have signed an Undertaking of Confidentiality form (refer to point 5, above). An invoice for the linkage work will be sent out, once the record linkage officer has received a confirmation that the researcher (data recipient) has successfully viewed the linkage results.

10. In order to respond to queries on the linkage results, the linkage data files will be retained by the AIHW for up to 12 months before being destroyed. Any further work requested for a project may result in an additional cost.

11. If AIHW is asked to undertake a ‘repeat’ linkage throughout the lifetime of the project, an additional AIHW Ethics Committee approval may not be required. Please specify upfront in the EthOS application if you intend to run an update or extended repeat linkage(s) over the lifetime of the project (refer to Section 3.1), noting that Committee approval is usually valid for seven years only. Please ensure that any new members of your research team who require access to NDI data sign an Undertaking of Confidentiality (s29 form) – refer to point 5, above.

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12. If your project requires and has approval to access Causes of Death (COD), please note that when DISC runs the NDI linkage for your project, COD data may not be available for all the ‘years of death’ that you require. Quite often COD codes will not be available for deaths that were registered at Births, Deaths and Marriages Registries (BDMR) in the most recent years. In general, there is a period of around 18 months until AIHW has access to COD data of recent deaths (e.g. COD data of deaths registered at BDMR in 2016 may only become available mid 2018 or later).

We can run the NDI linkage even if COD data is missing for one or more of the years of death required (e.g. 2016). We can still provide you with fact of death (including date of death) information of deaths that have been registered up to about a month before the linkage is undertaken. Upon request, DISC can extract COD for records that linked to the NDI and were missing COD data at the time the NDI linkage was undertaken, once COD data of the relevant death years becomes available.

To find out which year of COD data is currently available for data linkage purposes, refer to the webpage http://www.aihw.gov.au/national-death-index/ .

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2. The National Death Index

2.1 What is the National Death Index? The National Death Index (NDI) is a database, housed at the Australian Institute of Health and Welfare, which contains records with a set of identifying information of deaths registered in Australia since 1980. The data is obtained from the Registrars of Births, Deaths and Marriages in each State and Territory. The Index is designed to facilitate the conduct of epidemiological studies and its use is strictly confined to health and medical research.

2.2 Objectives of the National Death Index There is an increasing demand throughout Australia for epidemiological studies to determine the relationships between environmental, occupational and life-style factors and chronic diseases.

The NDI allows a quick and efficient electronic search of deaths registered in Australia since 1980. Researchers can request approval to link their dataset of patients or study population to the NDI. Personal details (such as Name, Sex, Date of Birth etc.) are used in the linkage process to determine who on the research dataset has potentially died.

2.3 Variables on the National Death Index The NDI is updated monthly except for cause of death information, which is usually updated annually. The NDI stores the following information of deceased persons:

Linkage variables: • Surname (including maiden names, where appropriate) • Given names (up to three given names) • Sex • Date of birth • Address at time of death (not all NDI records have address or it may be incomplete)

Fact of Death (FOD) variables: • Date of death • State/Territory where death was registered • Year of death registration

Cause of Death (COD) variables: • Underlying cause of death (as ICD9 codes until 1996, as ICD10 since 1997) • Other causes of death (as ICD10 codes since 1997)

Other variables: • Indigenous status • Marital status • Region of address at time of death

To improve the quality of the linkage results, please provide as much information as possible in relation to the variables that we require for linkage (refer to Section 4.3).

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Section 4.6 describes the variables we provide with your linkage results. Please note that underlying cause of death and other causes of death codes are NOT automatically included in the NDI linkage results provided to clients. If you require cause of death data, your ethics application must state why you require cause of death codes and how you will use the data in your study. The AIHW Ethics Committee will have to approve the release of those variables with your NDI linkage results.

2.3.1 Additional variables Some additional variables (e.g. postcode) can sometimes be included in the proposed linkage results. If you require any special variables, please discuss availability of them with the AIHW record linkage officer before submitting the ethics application. Additional variables requested after your EthOS application has been approved is likely to require separate Ethics Committee approval. You may be able to request the approval using an amendment form. Please contact [email protected] for advice.

2.4 How is the National Death Index maintained? The AIHW is responsible for the ongoing management of the NDI. The NDI consists of Fact of Death (FOD), which includes Date of Death (DOD) and Cause of Death (COD) information. FOD (including DOD) information is updated monthly from files provided by each State/Territory Births, Deaths and Marriages (BDM) Registrar. However, COD information is only updated once a year, with new information supplied by the Australian Coordinating Registry (ACR, for the Registrars of BDM) and the National Coronial Information System (NCIS), after coding by the Australian Bureau of Statistics (ABS). Due to the processes involved in generating COD information, the ACR generally supplies the data to AIHW approximately 18 months after the completion of the relevant calendar year (e.g. 2014 COD provided mid 2016). However, further delays may be encountered which are beyond the AIHW’s control.

2.5 Confidentiality of data The Australian Institute of Health and Welfare Act 1987, as amended in 1989, obliges the AIHW to enforce any conditions attached to the supply of data to the Institute. As Australian Government officers, the release of information by AIHW staff is also controlled by the Privacy Act 1988, Public Service Regulations and the Commonwealth Crimes Act.

There is an agreement between AIHW and the Registrars of Births, Deaths and Marriages, which covers the restrictions on the use and release of the information provided. Under this agreement, the Registrars are regularly notified of all NDI linkage projects. A Registrar is a member of the AIHW Ethics Committee.

The confidentiality conditions of the Australian Institute of Health and Welfare Act 1987 also apply to data provided by NDI users.

2.6 Security The AIHW maintains a secure physical and computer environment for the NDI and for datasets provided by researchers to link to the NDI.

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3. Preparing an AIHW ethics application to obtain approval to access NDI data As mentioned in Section 1, before applying for a NDI linkage or discussing with AIHW staff how to submit the data file to link to the NDI:

• Ensure your project is in scope and that you have enough variables to enable a successful linkage. Please contact DISC if you have any questions. • If required, obtain a preliminary quote from the AIHW data linkage officer on the costs of the linkage to include in your funding application. • Applications need to be submitted using the Ethics Online System (EthOS). • For information on AIHW Ethics Committee meeting dates, due dates for submission of applications and how to obtain assistance with the EthOS application, refer to the webpage www.aihw.gov.au/ethics/.

3.1 Important points to consider when completing the DISC related aspects of an ethics application Before finalising or submitting your application to the AIHW Ethics Committee, please consider the following important points:

• Specify the number of records you require to link to the NDI, and the time period the records were collected. For example, approximately 5,000 cardiac hospital inpatients between 1 January 2010 and 31 December 2015. • Explain how the NDI data will be used, for example: - To ensure that no deceased persons are contacted in the follow-up study; or - To analyse survival rates and mortality outcomes. • Mention any special features affecting the linking of your data file to the NDI. For example your project might involve using truncated names (e.g. modified 3-letter- surnames) rather than full names in the linkage. • Specify the NDI variables required. For example, fact of death, date of death and all causes of death. Only variables needed should be requested. • State clearly in the application if you require access to underlying or all causes of death information. You will also need to explain how cause of death data will be used. • Are you planning to measure longer term mortality outcomes? If so, you may require ‘repeat’ linkages to the NDI throughout the lifetime of the project. If your project requires repeat linkages please specify when you plan to run a repeat linkage. For example, you may require: - Repeat annual linkages on an ongoing basis; or - A current linkage with a follow-up linkage in 5 or 7 years. Please specify if your repeat linkage involves: - An update linkage, where the same dataset is used as in the previous linkage (excluding deaths previously identified), to obtain an update on who has died since the last linkage was undertaken (i.e. there are no new records and no change of scope);

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- An extended linkage, where the dataset contains the same records used in the previous linkage (excluding deaths previously identified) but includes additional records within the same scope, e.g. new patients added to the hospital registry with the same health condition (i.e. there are some new records but no change of scope); or - A new linkage where the dataset has changed or has a revised scope. Please note that any change in scope of a study will require submitting a new application and obtaining ethics approval. Generally there will be a change of scope should you change your analysis plan, which may lead to a request for one or more new variables or a change in the population of interest. Please discuss with DISC if you are unsure whether your scope is about to change. The request to undertake repeat linkages is important to mention in the application, as it will allow your future linkages to be handled more efficiently. • Please note that if you don’t have explicit consent from participants of the project or study to link their data to other databases, you will need to formally request a waiver of consent in the ethics application. For assistance in completing this part of the EthOS form (Section 3) please refer to the guidance provided with the application form or contact [email protected]. • Specify how you will protect the NDI data that you will receive. • Specify when and how you will destroy the NDI data and project files. • Specify a realistic ‘project completion date’ to ensure that you have valid and ongoing ethics approval for the lifetime of your project. The project completion date must include sufficient time to enable final publication of results and data destruction. Often researchers find that their project’s AIHW ethics approval expires prior to the completion date specified in the application. This is particularly the case for projects that request repeat linkages throughout the lifetime of the project or projects that require access to cause of death (COD) data. As mentioned under Section 1.12, there may be a lag of a year or more between researchers receiving NDI linkage results for their project (where COD data is often missing for certain death years) and the researcher receiving access to all COD data of the deceased persons on the project’s cohort file. There is additional time required until researchers can receive, analyse and publish on COD data that was missing. If your project requires COD data, we recommend that you factor in the extra time required (we suggest at least 2 years) to obtain and publish on missing COD data, when you specify the ‘project completion date’ in your application. Ensure signatures of all persons requiring access to NDI data are included with the application (refer to Section 1.5). • To avoid delays in obtaining data, ensure all necessary paperwork (e.g. approvals required from different jurisdictions, peer reviews etc.) is included with the EthOS application.

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4. How to provide data to the AIHW to link to the National Death Index

4.1 Introduction Once your project has obtained full approval for data linkage from the AIHW Ethics Committee (Section 1.3), please contact the Data Integration Services Centre (DISC) at AIHW to obtain instructions how to format the dataset and to receive a template to use to submit the data for linkage. You will also require access to the AIHW Secure Messaging system (ASM) to securely transfer the data file to DISC.

No linkage work will commence until final approval from the Committee has been provided. In some instances the Committee may give conditional approval, which means that additional information and/or clarification of various aspects of the proposed research (linkage work) needs to be provided before final approval can be granted. If this applies to your project, you will be asked to provide extra information, which the Committee will consider and you will be notified of the outcome via a letter. Linkage work will only commence once you have received a final, full approval letter.

Please do not send the data to DISC, until you have received full approval from the Committee, instructions how to format the data file and access to ASM.

Sections 4.2 and 4.3 describe the variables that are required to run a NDI linkage and how to submit a data file to DISC. Meeting these specifications as closely as possible will assist in reducing the time and cost of your linkage request.

4.2 How the data file should be sent for linkage The AIHW prefers to receive your data as an Excel file (or for large datasets as a quote encapsulated comma separated value text file (.csv)). If you are unable to provide your data in this form or if the file is very large, please contact DISC to discuss other options. When you are ready to submit the file please contact DISC at [email protected] to arrange access to ASM. A record linkage officer will establish an ASM account for you to enable you to securely transfer the data to DISC. The data file needs to be encrypted and password-protected, before emailing it to the record linkage officer via the ASM account. The password must be sent in a separate email or you can telephone the data linkage officer to inform them of the password. If the data file cannot be sent to DISC electronically, you can use a physical medium, such as CD, DVD or USB to send the data. Please encrypt and password-protect the data before transferring it to the medium. The data can be delivered to: Data Integration Services Centre (private and confidential) Australian Institute of Health and Welfare GPO Box 570 Canberra ACT 2601 Please do not include the password with the CD, DVD or USB. It is in your interest to format your data file according to our instructions to minimise completion time for the project. If extensive correspondence and/or data cleaning are needed before the linkage can commence, we will charge an additional fee.

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4.3 Variables to provide for linkage and how they need to be formatted

4.3.1 Variables to provide You should provide as many of the following items as possible: • ID Number (IDNUM, a unique record identifier for your use) • Link ID (if you have duplicate records relating to the same person) • Surname • First given name • Second given name (or initial of middle name) • Third given name • Sex • Date of birth • Date of last contact (for example, date of last known discharge from hospital) • State of residence at last contact • Death Status (specify D for deceased, if the person is known to have died) • Date of death (if known) • Address at last contact (if available) • Multiple births flag (if available)

The minimum variables required to undertake a standard NDI linkage are: Surname, First given name, Sex and Date of Birth. If you have less information, such as truncated names (i.e. only a few characters of Surnames and First given names), please contact DISC to discuss your project.

If a person is known to have died but the date of death is unknown, please specify D in the Death Status column to indicate that the person is deceased. You may also supply additional variables that you have, which could be useful for clerical review purposes (e.g. to provide address or to indicate that a date of birth of a record was estimated).

4.3.2 Format of variables 4.3.2.1 Record Identifying Number (IDNUM) This variable is assigned by you to help you identify your own records. It can be in any format. Please do NOT use a confidential identifier number such as a hospital patient number or Medicare number which can be used to link to personal medical information. Instead, please assign a new and unique identifier for each record.

4.3.2.2 Link ID Where individuals are known to have duplicate records, please create an additional variable called Link ID. While IDNUM should be unique to each record, Link ID should be unique to a person. The dataset may include duplicate records of the same person to maximise the likelihood of linking the person to a record on the NDI. The value of Link ID must be the same in multiple records of the same person. An example of using Link ID would be where a female has different surnames. In one record her surname would specify the married name while in another record her maiden name is the surname. For more information on Link ID, refer to the description below under ‘Alternate names’.

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4.3.2.3 Names Put each name in a separate field, i.e. do not put them in one field separated by blanks (except for the Given Name 3 cell). Delete words or titles such as Brother, Sister, Father, Senior, Junior, Baby of, Dr, Professor etc. (and their abbreviations). Do not submit fields containing a name followed by a different name in parentheses. If the name in parentheses is a well-known variant, delete it entirely. For example, “Robert (Bob)” should be just “Robert” or “Bob”. If the name in parentheses seems rather different, you can shift it to the next available blank name cell or duplicate the record (refer to information in the next paragraph).

Alternate names. If you have a person with two or more surnames (or on a rare occasion alternate given names) and you are not sure how the deceased person’s information is stored on the NDI, you can duplicate the person’s record and use a different name in each version of the record. For example, if you have Mary Smith (nee Brown) and you wish to search for both variants, you can split this into two records: one Mary Smith and one Mary Brown. You might want to adjust the identifying number (IDNUM) of the original record to reflect its variants. IDNUM should be unique to each record. To make IDNUM unique, you could append an “A” to IDNUM of the first variant and a “B” to the second or append _1 and _2 respectively. Please note that adding an alternate name record may create duplicate proposed links in your results. As mentioned above, please include a Link ID for duplicate records and assign the same value in Link ID for multiple records relating to the same person.

Below is an example of cohort records. There are duplicate records for Mary with different IDNUMs but same LinkID. There is only a single record for Peter.

IDNUM LinkID Surname Given Name 1 etc. (unique to each record) (unique to each person) 118 118 Baker Peter 123A or 123_1 123 Smith Mary 123B or 123_2 123 Brown Mary

4.3.2.4 Sex Use “M” for male, “F” for female, and blank for unknown.

4.3.2.5 Dates We require dates to appear in yyyymmdd format, for example 19650531 for 31st May 1965. There are 3 ways to store dates in this format:

Option 1: If your date data is stored as an Excel date (for example as 31/5/1965 or 31 May 1965 etc.) change the format to Custom yyyymmdd, using the Format Cells option which can be accessed by clicking on the drop down arrow in the “Number” group on the Excel ribbon and then selecting ‘More Number Formats’(see example below).

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Press the ‘OK’ box to change the format to Custom yyyymmdd.

Option 2: Store your date data as a number, e.g. 19650531

Option 3: Store your date data as an 8 character text string, e.g. “19650531”

Dates preceding 1900. Excel is unable to handle dates that precede 1900. If you have any such dates please store them in the format as described above under Option 2 or 3.

Date of birth and date of death. If you have incomplete dates, leave the unknown portions blank rather than filling them with dummy values. That is, use 193312 rather than 19331215 if the day is unknown. This makes some decisions in the clerical review a little easier. For example, a cohort death date of 201607 compared to an NDI death date of 20160721 seems a slightly more reasonable link than if the former was 20160715. However, we realize that Excel cannot store dates with missing components in an Excel date format. In this case it is better to store an incomplete date as a number or as a text string, as mentioned under Options 2 and 3 above.

Date of last contact. A date of last contact can be supplied. It is the most recent date that the person was known to be alive. If you have never had any follow-up contact with the person, use the date he/she was recruited into your cohort or their date of birth as a last

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resort. You may have an individual date of last contact for each person in your cohort or you may have a single date that applies to all people. If only the year is known, use the 1st of January of that year. Where available, DISC uses date of last contact to help verify linkage results.

4.3.2.6 State of residence at last contact This item is not required for the linkage but is useful to have when undertaking the clerical review (i.e. when reviewing each record pair to decide whether to accept or reject the link). State of residence is compared with State the death was registered in. The NDI uses the standard 2- and 3-letter abbreviations (e.g. WA, ACT, NT etc.). We recommend that you use the same abbreviations, with ‘Overseas’ abbreviated as ‘OS’.

4.3.2.7 Address at last contact This information is not required for the linkage but is very useful to have when undertaking the clerical review.

4.3.2.8 Multiple births flag This flag is not required for the linkage but is useful to have when undertaking the clerical review. Enter a ‘1’ (without quotes) if the person’s birth was one of multiple births (e.g. person is a twin). Otherwise, leave the field blank.

4.4 AIHW receiving your data When the Data Integration Services Centre (DISC) receives your data through the AIHW Secure Messaging (ASM) system, we will send you an email to acknowledge that we have received the dataset and to confirm the number of records contained in the data file. Your project will be added to our queue of linkage requests. We will contact you once we are ready to start on your project. There can be a delay of a few weeks between DISC receiving your dataset and DISC starting on your linkage request. It depends on the number of other projects we are working on at that time.

When work on your project commences, the dataset will go through a data cleaning process to prepare the dataset for linkage. If there are too many data issues that need to be resolved before we can use it in the linkage, we will ask you to amend the data file and to re-supply the data to us. We will have to charge you an additional cost for ‘data cleaning’ should we require a significant amount of time to prepare the data file for linkage.

4.5 Final quote Once we have checked the data file, a final quote will be sent to you by email which must be accepted before the linkage process commences. As mentioned under the Guide/Checklist of Section 1, the minimum cost of a standard, single NDI linkage is $3,500 (exclusive of GST). The cost assumes that DISC: • Receives the data file from a single source (i.e. the data file is sent to DISC from 1 data provider) • Undertakes minimum data cleaning, before preparing the data for linkage

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• Runs the NDI linkage (using full Date of Birth) on a single cohort • Provides the linkage results to a (1) data recipient (researcher) in the standard format. The assumption is that a researcher undertakes the clerical review work. • Provides Date of Death and Cause of Death data in the results (if approved by the Ethics Committee) • Extracts Cause of Death (COD) data once (when the data becomes available), after a NDI linkage has been completed, to provide the researcher with COD codes that were missing at the time the linkage was run (refer to Section 2.4). If any of the above-mentioned points differ (e.g. AIHW is requested to undertake the clerical review), the cost of the NDI linkage may increase. The cost excludes the ethics administration fee which is charged when an application is submitted. For projects that have repeat (or ongoing) linkages approved, a linkage fee is charged separately each time we complete a linkage request.

If at a later date you require DISC to undertake additional work, a quote for the additional task and the timeframe to complete the task will be provided to you. You will need to approve the additional cost before we can commence the extra work.

As mentioned in Section 2.4, there is often a delay in accessing Cause of Death data (COD) that wasn’t available when the linkage was run. To find out which year of COD data is currently available, refer to the webpage http://www.aihw.gov.au/national- death-index/ .

If your project obtains approval to access COD data, please note that DISC provides one (1) free extraction or update on COD data after a NDI linkage was undertaken. The extraction can relate to records that were missing COD data at the time the linkage was undertaken or can relate to a request to obtain updated COD data. Any additional COD extractions requested (beyond the ‘free one’ we provide) may incur an extraction fee. You may have to wait up to 18 months until COD data becomes available for the most recent year range you are interested in. You may decide to delay requesting the ‘free extraction’ until we have received COD of a particular year. For example, if your data has acceptable (good) links to NDI records of deaths that were registered in 2016, COD information for those deaths may not become available until mid 2018 or later.

4.6 Receiving the results The following standard NDI variables can be released to researchers, subject to AIHW Ethics approval: • The weight of the linked record pair • Date of death • State i.e. State of residence at last contact (from your cohort) and the State the death was registered in (from NDI) • Year the death was registered in (NDI only) • ID number i.e. IDNUM (from your cohort file), Link ID (if provided) and NDI ID • Underlying cause of death (if requested and approved by AIHW Ethics Committee) • Other causes of death (if requested and approved by AIHW Ethics Committee)

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After running the NDI linkage, researchers quite often review the record pairs (i.e. the links between cohort and NDI records) and decide whether to accept or reject the links. The process of reviewing record pairs is called ‘clerical review’. We recommend researchers to undertake the clerical review, unless they are not permitted to view identifiable data (such as Names, Sex, Date of Birth etc.). DISC can undertake the clerical review at a cost which is dependent on the number of records that need to be clerically reviewed. Documentation on clerically reviewing the record pairs is included in the user guide that the record linkage officer sends out with the NDI linkage results. Further assistance in reviewing record pairs may be obtained from DISC staff.

If DISC undertakes the clerical review then identifying information such as names or full dates may not be provided to researchers. Ethics approvals or data linkage protocols may specify certain conditions relating to the release of data to researchers. For example, AIHW may not provide names of study participants to researchers or may only release month and year of dates.

If the researcher has permission to view identifiable data and undertakes the clerical review, the result files also include the following cohort, linkage and diagnostic variables: • Warning flags for the linked record pair • Surname • First given name • Second given name • Third given name • Sex • Date of birth • Birth dummy flag (NDI only) • Date of last contact (from cohort file only) • Death status (from cohort file only) • Death dummy flag (NDI only) • Address, if provided i.e. Address at last contact (from cohort file) and the Address at time of death (from NDI) • Multiple births flag (from cohort file only, if provided)

The result files are emailed to a researcher through our secure messaging system (ASM), as an encrypted and password-protected file. Please note that we can only send the linkage results to persons who have signed an Undertaking of Confidentiality (s29 form, please refer to Section 1.5). In a separate email, we send the password to open the zip file with the linkage results and ask the data recipient to install PeaZip (or ‘StuffIt-Expander’ for Mac computers) on their computer to enable them to extract and install the result files onto their computer. Both types of can be downloaded for free. The email includes a user-guide that describes the linkage results and provides some information on the clerical review (if researchers undertake the clerical review).

Linking Research Data Files to the National Death Index (NDI) September 2016 Page 16